In radio communication, provision is generally made for transmit data to be encoded before transmission in order to increase error correction capability. One such encoding method is LDPC encoding such as described in Non-patent Document 1. Since this LDPC encoding enables error correction to be performed using an extremely large block unit (constraint length), it is considered to be resilient to burst errors, and suitable for communication in a fading environment.
Also, a multi-antenna transmitting apparatus that transmits OFDM signals from a plurality of antennas, such as described in Non-patent Document 2, is known as a technology for increasing data transmission speed. With such a multi-antenna transmitting apparatus, interleaving data in a plurality of frequency directions (subcarrier directions) has been proposed as one method of suppressing burst errors due to frequency selective fading.
FIG. 1 shows an example of the frame configuration of a transmit signal in such a multi-antenna transmitting apparatus. In FIG. 1, distortion due to fading fluctuation—that is, a channel estimate—and a preamble for estimating frequency offset between a transmitter and receiver, are placed at the start of a frame, and data symbols are placed thereafter. Also, pilot symbols for estimating frequency offset, which fluctuates over time, are placed on carrier Y. In FIG. 1, one square indicates one symbol. That is to say, in the example shown in FIG. 1, one OFDM symbol composed of a total of 7 symbols—data symbols and a pilot—is transmitted at each of times i, i+1, . . . . At this time, data are interleaved within one OFDM symbol, and placed in the order (1) (2) (3) . . . (11) (12).    Non-patent Document 1: “Low-Density Parity-Check Code and Decoding Method LDPC (Low Density Parity) Code/Sum-Product Decoding Method” Triceps 2002    Non-patent Document 2: 2High Speed Physical Layer (PHY) in 5 GHz band” IEEE802.11a 1999.    Non-patent Document 3: B. Lu, G. Yue, and X. Wang, “Performance analysis and design optimization of LDPC-coded MIMO OFDM systems” IEEE Trans. Signal Processing, vol. 52, no. 2, pp. 348-361, February 2004    Non-patent Document 4: B. M. Hochwald, and S. ten Brink, “Achieving near-capacity on a multiple-antenna channel” IEEE Trans. Commun., vol. 51, no. 3, pp. 389-399, March 2003    Non-patent Document 5: S. Bäro, J. Hagenauer, and M. Witzke, “Iterative detection of MIMO transmission using a list-sequential (LISS) detector” Proc. of IEEE ICC 2003, May 2003    Non-patent Document 6: B. M. Hochwald, and S. ten Brink, “Achieving near-capacity on a multiple-antenna channel” IEEE Trans. Commun., vol. 51, no. 3, pp. 389-399, March 2003    Non-patent Document 7: S. Bäro, J. Hagenauer, and M. Witzke, “Iterative detection of MIMO transmission using a list-sequential (LISS) detector” Proc. of IEEE ICC 2003, May 2003    Non-patent Document 8: P. Robertson, E. Villebrun, and P. Holler, “A comparison of optimal and sub-optimal MAP decoding algorithms in the log domain” Proc. IEEE ICC 1995, pp. 1009-1013, June 1995    Non-patent Document 9: K. Kobayashi, Y. Murakami, M. Orihashi, and T. Matsuoka, “Varying interleave patterns with iterative decoding for improved performance in MIMO systems” Proc. of IEEE PIMRC2004, vol. 2, pp. 1429-1433, September 2004    Non-patent Document 10: T. Ohgane, T. Nishimura, and Y. Ogawa, “Applications of space division multiplexing and those performance in a MIMO channel,” IEICE Trans. Commun., vol. E88-B, no. 5, pp. 1843-1851, May 2005    Non-patent Document 11: “Digital Wireless Transmission Technology” Pearson Education    Non-patent Document 12: “Convolutional Code Maximal Likelihood Decoding and Its Characteristics” Technical Report of IEICE A Vol. J73-A No. 2 pp. 218-224